Stoptech's big brake upgrade for the S4 and A6 does not
include the parts or instructions necessary to enable the "worn brake"
indicator used by the stock brakes. Instead, Stoptech's installation
instructions teach cutting the sensors from the pad and shorting the exposed
wires in order to disable the worn brake indicator. As you will see from the
instructions that follow, it is not difficult to modify the stock sensor plug
harnesses to use Porsche brake pad wear sensors and retain the functionality of
the stock worn brake indicator.

Given Stoptech's use of readily-available Porsche
compatible brake pads, it occurred to me that Porsche brake pad wear sensors
might solve this shortcoming of the Stoptech brake system. A search of the
AudiWorld archives revealed Ming 2.7T's September 2002 post containing
pictures of his Stoptech installation that show his use of Porsche brake pad
wear sensors to enable the worn brake indicator in his A6.

As shown at right, after a relatively
simple installation, the sensors work perfectly. The instructions below
are designed to replace Step 13 in the Stoptech installation instructions
(or Steps 10 and 11 in the APR Level 3 Brake Installation Manual).

Parts Needed:

2 - Porsche Brake Pad Wear Sensors from a 1989-91
Porsche 928 - Part Number 928 612 365 01 - These can be purchased
from any Porsche dealer (suggested retail is $18/each) or from The
Tech Group in Northern California (650-610-0555) for $15/each (ask for
Donna and tell her I sent you). A picture of the appropriate Porsche
brake pad wear sensor is shown at right.

4 - 1" pieces of 1/16" Heat Shrink Tubing

2 - 3" pieces of 1/4" Heat Shrink Tubing

Solder

Tools Needed:

Wire Cutters

Wire Stripper

Soldering Iron Lighter or Heat Gun

Step 13 Modify Brake Wear Sensor:

In order to enable the "Worn Brake" indicator
light, the brake pad wear sensor from the stock sensor plug harness needs to be
replaced with a Porsche brake pad wear sensor and re-installed.

Prepare Stock Sensor Plug Harnesses:

- Cut the stock sensors from the two stock pad wear sensor
harnesses leaving approximately 1 ½" of both wires behind the plug on each
harness, as shown at right. I refer to this piece as a "stock sensor plug
harness" below.

- Discard the stock sensors (or leave them on the
stock pads/calipers).

- Strip approximately ½ inch off the
outer insulation from each of the two stock sensor plug harnesses and 1/4
inch of insulation from each of the inner wires on the two stock sensor
plug harnesses (four wires total). One of the stock sensor plug harnesses,
with its insulation stripped is shown at right.

Prepare Porsche Wear Sensors:

- Cut the Porsche pad wear sensors from the two Porsche
sensor plug harnesses leaving approximately 1 ½" of both wires behind the
plug on each harness. The picture at right shows one harness after I had
stripped the insulation. I refer to this piece as a "Porsche pad wear sensor"
below.

- Discard the harnesses.

- Strip approximately ½ inch of the outer
insulation from each of the two Porsche pad wear sensors and 1/4 inch of
insulation from each of the inner wires on the two Porsche pad wear sensors
(four wires total). One of the Porsche pad wear sensors with its insulation
stripped is shown at right.

- Slip one piece of 1/4" heat shrink tubing onto each of
the two stock sensor plug harnesses.

- Solder the wires on the stock sensor plug harness onto
the wires on the Porsche pad wear sensors (four wires total). It does not appear
to matter which wire is soldered to which.

- Slide the 1/16" heat shrink tubing over the soldered
connections on each of the four soldered wires such that there is no exposed
wire that could short, and melt the heat shrink tubing into place.

- Slide the 1/4" heat shrink tubing
over the previously heat shrunk wires on each harness and melt into place
to seal the entire length of wires with the heat shrink tubing. A picture
of the completed harness, which I refer to as the "Porsche/Audi Sensor
Harness" below is shown at right.

Install The Custom Porsche/Audi Sensor Harnesses:

- Plug the Audi end of each Porsche/Audi Sensor Harness
into the mating connectors on the car's wiring harness and dress the sensor
wire to the brake line using the supplied high temperature ty-wraps (see Step 2
above (or Step 9 in APR Manual)).

-Plug the
Porsche pad wear sensors into both brake pads on both sides of the car as
shown at right.